Heretofore, in the production of vitamin B12 from propionibacteria, methanol is used as a substrate and the growth of these bacteria is very slow because these bacteria are facultative anaerobe. Also, because propionic acid is transformed into acetic acid, and the acetic acid caused growth inhibition. So that the density of cell bodies in fermented liquor is not increased and the amount of vitamin B12 that can be extracted from the cell body is the order of 1 mg/L, showing that the conventional process has low productivity. And Shiro Nagahisa et al. (Seibutsu-kogaku Kaishi, 76(6), 447–455, 1998) used an immobilized bed bioreactor of methane bacteria wherein methanol is used as a substrate to compare the yield of vitamin B12 of methane bacteria with that of propionibacteria and obtained vitamin B12 from methane bacteria in a yield 10 times higher than that obtained from propionibacteria. However, the resulting solution contains, as its major component, collinoid having small cobalamin types. In this case, there is the problem that the recovery of vitamin B12 is not improved because a process of separation from methanol is complicated and this method does not bring about a reduction in production cost since the content of vitamin B12 is small.